GB586594A - Improvements in or relating to reflex reflectors suitable for road or advertising markers - Google Patents

Abstract

586,594. Coated fabrics. MINNESOTA MINING & MANUFACTURING CO. Nov. 8, 1943, No. 18528. Convention date, Jan. 23. [Class 140] [Also in Groups XVIII and XX] In a reflex reflector of the kind comprising a layer of small transparent spheres 14, Fig. 1, adhesively secured to a reflecting backing 10, 11, the spheres are partly embedded in an adhesive 13 which contains a reflecting pigment, and make contact on their rear surfaces with a transparent layer 12 which spaces them from the backing, so that rays c approximately normal to the surface pass through the spheres to the rejecting backing, whilst rays b at an acute angle are reflected from that zone of the interior of the spheres which contacts the pigmented adhesive. The reflecting backing and the pigmented adhesive may be differently coloured, so that the colour of a road or advertising sign illuminated at night by car headlamps changes from that of the backing to that of the adhesive layer as the car approaches the sign and the angle of incidence of the rays becomes more acute. The transparent spacing layer 12 may be overlaid with another transparent layer 18, Fig. 2, in which the spheres are partly embedded to ensure a good optical communication with the backing. The backing may be aluminium foil, or waterproofed paper 10 or a non- fibrous film, e.g., of polyvinyl butyral coated with a varnish 11 containing aluminium flakes or white or coloured pigment. The varnish may be a solution of polyvinyl butyral resin. The transparent spacing layer 12, Fig. 1, may be a solution in an aromatic hydrocarbon solvent of a drying-oil modified alkyd resin which is cured before the spheres are applied. The thin transparent coat 18, Fig. 2, may be a solution of a urea-formaldehyde resin, a glycerol phthalate resin, and a plasticizer such as castor oil or ricinoleic acid. The reflective binder comprises the composition used for the transparent spacing layer with added pigment such as titanium dioxide. The transparent spheres are applied while the transparent coat. 18 and reflective binder are soft, the surplus spheres are removed to leave a single layer, the sheet is nipped between rollers to force the spheres into the surface of the transparent spacing layer, and the sheet is cured by heating at 185‹F. for 24 hours. Specification 586,595 is referred to.